Crystalline growth and alloying of InxGa1-xSb films by electrodeposition onto liquid metal electrodes

Incorporating indium (In) atoms into the GaSb lattice provides broad tunability of the optical bandgap within the infrared spectral region. This research documents the first instance in the literature of electrochemical liquid-liquid-solid (ec-LLS) growth of a ternary semiconductor alloy. Indium content of deposited InxGa1-xSb samples was regulated by controlling the Ga/In ratio of the liquid metal electrode. All depositions were performed using a single-step growth method under ambient pressure at 90 +/- 5 degrees C. X-ray diffraction analysis showed shifts of the (111) diffraction peaks toward the peak locations of cubic InSb for the x = 0.50, 0.60, and 0.70 samples, indicating a consistent increase in lattice parameter. However, the x = 0.28 and 0.41 samples displayed unexpected shifts toward larger angles, possibly due to increased presence of Ga vacancies and antisites caused by Ga-rich growth conditions, as well as insufficient mixing of the liquid metal electrode for x < 0.50. Optical bandgaps ranging from 0.594 to 0.707 eV were determined via the Tauc method and Kubelka-Munk theory applied to diffuse reflectance data, and showed general agreement with measured lattice constants. Data obtained in this research supports In incorporation into the GaSb lattice for samples with x >= 0.50, but with significantly lower In compositions relative to the liquid metal electrode. No general trend was observed for average crystallite size as a function of In composition, likely due to inconsistencies in the film harvesting process. This research provides further support for ec-LLS as a semiconductor growth technique capable of crystalline growth and alloying of III-V semiconductors.